Final answer:
Bacteria adapt to environmental changes with cell walls that handle osmotic stress, form heat- and drought-resistant endospores, and develop antibiotic resistance through mutation and horizontal gene transfer.
Step-by-step explanation:
An individual bacterium copes with environmental changes through a variety of adaptations and mechanisms. Almost all prokaryotes, which include bacteria, have a cell wall that allows them to survive in different osmotic conditions, whether hyper- or hypo-osmotic. Some bacteria can form endospores, which are highly resistant to extreme conditions like heat and drought, lying dormant until conditions improve. In response to the presence of antibiotics, bacteria can undergo natural selection, which often leads to the development of antibiotic resistance. This resistance is achieved through mutation and is spread among bacteria through horizontal gene transfer, allowing them to survive in what would otherwise be deadly conditions.